What it is
Melanotan II is a peptide made of 7 amino acids joined in a ring. It is made in a lab. It copies alpha-MSH, the hormone that tells skin cells to make dark pigment. Scientists at the University of Arizona built it in the late 1980s. It turns on four melanocortin receptors at once: MC1R, which controls skin pigment, MC3R and MC4R, which affect sexual response and appetite, and MC5R. Because it hits so many receptors, it has many side effects. It has never been approved in any country. PT-141 was made from it. Other names: MT-II, MT-2, Melanotan 2.
What researchers study it for
- Skin darkening without sun exposure
- Erection response in men
- Appetite and body weight in animals
- How the peptide spreads through the body in rodents
- Melanocortin receptor research
What the studies found
1. Skin darkened in the first human study.
A 1996 study gave healthy men shots under the skin at rising doses. Skin pigment, measured with a light meter, went up as the dose went up. Some men also had erections without any sexual trigger. Common side effects were nausea, face flushing, and tiredness. This was a small early safety study in humans.
2. Men with erectile problems had erections after treatment.
Ten men whose erection problems had no physical cause got Melanotan II and a placebo on different days. Eight of the ten had erections measured by a device. Nausea, yawning, and stretching were the main side effects. This finding led directly to the development of PT-141.
3. The MC1R receptor is what controls tanning.
This 1999 review explains how skin pigment is made. Alpha-MSH attaches to MC1R on pigment cells, called melanocytes. That tells the cells to make eumelanin, the dark pigment. People with certain versions of the MC1R gene have red hair and tan poorly. This is the receptor Melanotan II turns on to darken skin.
4. Very little of it reached the mouse brain.
Mice got Melanotan II by injection into the belly. It left the blood quickly. Thirty minutes later, brain levels were low even though blood levels were high. Researchers still do not know exactly how it causes effects controlled by the brain, like nausea and appetite changes. One idea is that it acts on brain areas that sit outside the blood-brain barrier.
5. No human study has measured how long it stays in the blood.
This study built a lab test to measure Melanotan II in rat blood after an IV dose. All timing data for Melanotan II comes from rats and mice. The human study measured skin color, not blood levels. The "about 1 hour" figure you see online comes from rodents, not people.
6. A related peptide went on to approval. Melanotan II did not.
This 2006 review was written by two of the scientists who developed Melanotan II. It traces the path from alpha-MSH to Melanotan II to PT-141. It lists nausea, face flushing, and tiredness as common side effects at higher doses. Of the peptides in this family, PT-141 and Melanotan I (afamelanotide) reached approval. Melanotan II stayed a research compound.
How much research exists
One small human safety study, one small erection study, and a number of rodent and lab studies. No large human trial has been published. It never went through drug approval.
Facts
- Formula: C50H69N15O9
- Weight: 1024.2 g/mol
- CAS number: 121062-08-6
- Sequence: Ac-Nle-cyclo(Asp-His-D-Phe-Arg-Trp-Lys)-NH2
- Time in the blood: never measured in humans. Rodent data shows fast clearance.
- Storage: freeze the dry powder away from light. Keep mixed solution in the fridge.
Legal status
Not approved by the FDA or any other agency for human use. The FDA and regulators in several other countries have warned against using it. Banned in sports by WADA under section S0, which covers drugs not approved for human use.
For research use only. Not for human use. Nothing here is medical advice.